1. Field of the Invention
This invention relates to water-containing paste-form detergents based on NaOH. To establish the required viscosity, the detergents contain glycols, glycol derivatives and/or certain alkanolamines.
Highly alkaline cleaners are now commercially available in various forms, for example as powders, granules, liquids, fused blocks or tablets.
Each of these forms has specific advantages and disadvantages for a particular application. Powders, granules or liquids have been successfully used for cleaning textile surfaces or for the manual mechanical cleaning of hard surfaces while tablets produced by compression molding or block-form detergents obtained by melting and subsequent cooling (fused blocks) are being increasingly used in addition to powders, granules or liquids for the machine cleaning of hard surfaces, for example for machine dishwashing. Tablets and fused blocks have the advantage over powders of accurate and simple dosing, do not emit any dust and are easy to handle.
These advantages can be utilized, for example, in domestic dishwashing machines, but above all in continuous institutional dishwashing machines where the articles to be cleaned pass through various washing zones.
It has now been found that tablets and fused blocks also have disadvantages. For example, tablets can break. Tablets damaged by breakage naturally no longer have the advantage of accurate dosing. Another problem with tablets is that the required solubility in water cannot always be guaranteed, i.e. tablets occasionally dissolve either too quickly or too slowly. In addition, both tablets and fused blocks require complicated production processes.
2. Discussion of the Related Art
Paste-form detergents have been described in the prior-art literature, for example in DE-OS 31 38 425. The rheological behavior of the detergents described in this document is gauged in such a way that a gel-like paste can be liquefied by application of mechanical forces, for example by shaking or squeezing, to a deformable storage container or tube or by means of a metering pump and can readily be expressed from a spray nozzle.
In the document in question, silicates are primarily used as alkali carriers whereas the detergents according to the present invention are intended to be paste-like and to be based on the very inexpensive raw material, sodium hydroxide, as the alkali carrier.
One of the difficulties of producing paste-form highly alkaline NaOH-containing detergents is that many thickeners are either not permanently alkali-stable, so that their thickening effect diminishes, or are unsuitable for economic reasons.
U.S. Pat. No. 3,607,764 describes solid glass cleaners which can be diluted to form a sprayable solution. The cleaners in question contain inter alia sodium or potassium hydroxide, sodium or potassium tripolyphosphate, sodium or potassium pyrophosphate, hydroxycarboxylic acid builders, a water-soluble nonionic surfactant, alkylene glycol ether and optionally sodium carbonate. There is no reference to a paste-like consistency on the lines of the present invention.
JA 84/182870 describes solutions of small quantities of alkali metal hydroxides (below 2% by weight) in glycols or alcohols which become viscous by neutralization with long-chain carboxylic acids, have a pH value in the range from 7 to 11 and may be used as a paste in the oiling of leather by addition of silicone oil.
JA 86/296098 describes a solid detergent containing caustic alkali, preferably LiOH, NaOH, KOH, mixed with alkanolamine and polyethylene glycol in specific ratios by weight, so that a solid detergent with a dry surface is obtained. This solid aggregate state also prevents the phase separation of polyethylene glycol.